A work machine which travels by wheels, such as a wheeled excavator or wheel loader, is provided with a forward/reverse control system which instructs forward, reverse or neutral of the work machine. This forward/reverse control system is a F-N-R lever unit, which includes a F-N-R lever sticking out below a steering wheel toward a right or left side from a steering column and instructs forward, reverse or neutral in accordance with an operation of the F-N-R lever. The F-N-R lever can be shifted to a forward position that instructs forward, a reverse position that instructs reverse, or a neutral position that instructs neutral, and which can be held at the forward position, reverse position or neutral position.
The work machine is also provided with a front attachment control lever arranged on a console, which is disposed on a right or left side of an operator's seat, to control a front attachment.
The F-N-R lever and the front attachment control lever are arranged in a positional relation such that, when the F-N-R lever sticks out, for example, to the left side from the steering column, the front attachment control lever is disposed in a right front of the operator's seat or that, when the F-N-R lever sticks out conversely to the right side from the steering column, the front attachment control lever is disposed in a left front of the operator's seat. In other words, the F-N-R lever and the front attachment control lever are disposed such that the F-N-R lever and the steering wheel can be operated by the same one hand while the front attachment control lever can be operated by the other one hand.
Upon performing front/reverse switching in the work machine constructed as described above, an operator places one of his hands on the steering wheel and the other hand on the front attachment control lever. Upon operating the F-N-R lever, the operator hence tends to let the one hand go off the steering wheel. From the standpoint of safety, however, it is not preferred to let go off the steering wheel.
Accordingly, the conventional forward/reverse control system disclosed in JP-A-11-268656 is provided, in addition to the above-mentioned F-N-R lever unit, with another forward/reverse control means that instructs forward, reverse or neutral of the work machine and also with a switching instruction means that instructs a switch from a first control state in which forward/reverse switching control is performed by the forward/reverse lever unit to a second control state in which forward/reverse switching control is performed by the another forward/reverse control means.
The another forward/reverse control means is composed of a forward switch that instructs forward, a reverse switch that instructs reverse, and a neutral switch that instructs neutral. These switches comprise pushbutton switches equipped with self-resetting pushbuttons. A forward button as the pushbutton of the forward switch, a reverse button as the pushbutton of the reverse switch, and a neutral button as the pushbutton of the neutral switch are disposed on a top portion of the front attachment control lever.
The switching instruction means comprises a pushbutton switch equipped with a self-resetting pushbutton. The switching button as the pushbutton of the switching instruction means is disposed on a top wall of a console located in the vicinity of the front attachment control lever.
The conventional forward/reverse control system is designed such that the first control state is switched to the second control state when a switch is instructed by the switching instruction means in a state that neutral has already been instructed by the forward/reverse lever unit. In other words, the conventional forward/reverse control system holds the first control state in a state that forward or reverse has already been instructed by the forward/reverse lever unit. The conventional forward/reverse control system is also designed such that the second control state is cancelled to return to the first control state when the forward/reverse lever unit is operated in the second control state instructed by the another reverse control means. In other words, the conventional forward/reverse control system is designed such that forward/reverse switching is performed by giving priority to an operation of the forward/reverse lever unit.
With the conventional forward/reverse control system constructed as described above, forward/reverse switching of the work machine can be effected by the other hand without letting the one hand go off the steering wheel. Even when the operator operates the forward/reverse lever unit in an instant, forward and reverse can be switched to each other.